Here you can find information regarding the assembly of the Toyota 1.8L engine. In this guide we will
start from the inside of the engine including the
crankshaft, connecting rods, and piston ring installation and then move outwards all the way to the pulley belt
system. Along the way correct procedures and torque specs
will be given to aid in the assembly of the engine. Feel free to start from the beggining and work your way
outwards or skip ahead to your current position in the engine for what you may need.
Crankshaft Main Caps Installation
The 1.8L engine block main bearing caps should be inspected for any defects or flaws before installation.
Be sure to lubricate the bearing surfaces prior to installation. Once prepared you can place the caps onto the crankshaft
and begin tightening the bolts down in a multi stage process. The first being 10 ft-lbs starting from the middle and going outwards.
The second time around you can go to 30 ft-lbs and then for the third time you do an additional 90 degree turn for each bolt.
Once finished you should be good to continue with the rest of the engine.
Toyota Prius 1.8L Main Cap Torque Specs : 30 ft-lbs + 90°
Piston and Connecting Rod Installation
To install the pistons and connecting rods you must first install the piston rings into each piston. Be careful
not to stretch the rings or break them during installation. Make sure to put the correct rings in the correct
positions, this can be determined by looking at
the instructions given with the new rings. Each ring manufacturer is different so be sure to check for your
specific rings. Once the rings have been installed you can now fit the connecting rod bearings into the end caps
and lube them up with oil or lithium grease. The piston can now be lowered into the cylinder, make sure the dot
or mark is facing the front of the engine and that you don't scratch the cylinder.
Once installed you can match the connecting rod caps with the correct rods and start to torque the connecting
rod bolts to 15 ft-lbs and then an additional 90 degree turn for each bolt. After all are done rotate the crank
to ensure all pistons move smoothly in and out of their cylinders and nothing binds.
Toyota Prius 1.8L Connecting Rod Torque Specs : 15 ft-lbs + 90°
Oil Pump Installation
When installing the oil pump be sure to use the proper sealant around the pump base if neccessary to ensure that oil pressure
doesn't drop due to leakage. After preparing the contact surfaces carefully
install the oil pump onto the crankshaft by aligning the crankshaft end with the hole on the center of the pump gear. Once
installed you can then place the bolts into the holes and tighten them down to 8 ft-lbs. The oil pickup tube on this engine then bolts up
to the bottom of the engine block through the use of 2 nuts. These nuts can be tightened down to 8 ft-lbs along with the tubes
retaining bolt.
Toyota Prius 1.8L Oil Pump Torque Specs : 8 ft-lbs
Toyota Prius 1.8L Oil Pickup Tube Torque Specs : 8 ft-lbs
Cylinder Head Installation
The first thing you must do when installing cylinder heads is to ensure both the block and head surfaces are
completely clean from dust, oil, and any debris. The next thing you must to is
to set the camshafts to their correct positions to prevent any valves from hitting pistons during installation
and torquing of the head bolts. Much the same you have to set the pistons to their correct
locations, typically this means putting the #1 piston to TDC or Top Dead Center. Once everything is ready you
can install the head gasket onto the engine block by aligning the alignment dowels.
Something I usually do is spray down the head gasket with some engine copper spray from permatex which you can
find here, this ensures that any gaps that could be present between the 2 surfaces gets filled with the
spray. It
also helps to transfer heat between the 2 metals. With the gasket in place you can set the cylinder head onto
the gasket and block, if needed have someone assist with this process as the head can be heavy
and you don't want to scratch anything or drop it! Once the head has been placed you will want to start
installing the head bolts to make sure it doesn't move. Be sure to buy new head bolts as many manufacturers
use TTY or Torque to Yield head bolts meaning they stretch during torqueing and cannot be used twice. Also make
sure to lubricate the bolts in clean engine oil before installing them into the head.
Once all the head bolts have been installed and finger tightened you can start the torqueing process, almost all
head bolts have a multi-step process for torqueing. The 1.8L starts off with 25 ft-lbs and
then requires you to back them off a full turn. Then you must torque them to
36 ft-lbs and then two 90 degree turns by going through each bolt with each step.
After torquing the heads are completely installed and you can now move to intalling the timing.
Toyota Prius 1.8L Cylinder Head Torque Specs : 36 ft-lbs + 90° + 90°
Timing Chain and Tensioner Installation
On the Toyota 1.8 engine the timing system is ran by the use of a timing chain. This chain system consists of a
sprocket on each camshaft, a tensioner, timing guides, and a crankshaft gear. Before the chain can be put into place
you need to make sure that all of the gears are in their proper positions. Make sure the timing sprockets on the camshafts
are tightened down to 40 ft-lbs. Also ensure that both camshafts are installed correctly and the bearing caps are tightened to 12 ft-lbs or 20 ft-lbs for the
No1 bearing cap or largest cap.
Once everything is in place you can start by placing
the chain onto the upper camshaft sprockets by aligning the painted marks on the chain with the dots on the sprockets. If they are
properly in place there should be 2 more dots on each sprocket facing the other dot as shown in the picture. On the crankshaft gear
simply align the painted chain mark with the crankshaft dot located on the engine block. Once all marks are aligned you can place the timing guides
in place and tighten them down to 8 ft-lbs. At this point the timing cover can be placed onto the engine block. Be sure to check that section
for information regarding this procedure. Once the cover is on the timing tensioner can be placed into the cover and torqued down to 8 ft-lbs.
Toyota Prius Camshaft Sprockets Torque Spec: 40 ft-lbs
Toyota Prius Crankshaft Position Sensor Torque Spec: 8 ft-lbs
Toyota Prius Camshaft Bearing Caps Torque Spec : 12 ft-lbs
Toyota Prius Camshaft Bearing Cap No1 Torque Spec : 20 ft-lbs
Toyota Prius Timing Guides Torque Spec : 8 ft-lbs
Toyota Prius Timing Tensioner Torque Spec : 8 ft-lbs
Timing Cover Installation
The timing cover on the 1.8L is used to cover up the timing chain and retain engine oil inside of the engine. For this reason I recommend using
a new timing cover gasket and some silicon sealant to ensure that the cover does not end up leaking. Once both contact surfaces have been cleaned
and the new gasket and silicon is in place and ready you can place the cover onto the engine and tighten down the cover bolts to about 10 ft-lbs.
This covers all of the fasteners that have 10mm heads. The single 12mm head bolt can be tightened down to 14 ft-lbs.
Toyota Prius Timing Cover Torque Specs : 10 ft-lbs
Oil Pan Installation
Much like the timing cover on the 1.8L the oil pan plays an important role in keeping the engine oil inside the
engine. For this reason I recommend using a new gasket as well as some silicone sealant
during installation. Using the same technique as before with the cover you clean the surfaces of both the oil
pan and the engine block and then install the new gasket onto the block and then follow
it up with some silicone sealant. Be sure to follow your sealants instructions to ensure you get the best seal
from your application. The oil pan bolts torque to 8 ft-lbs in a cross
pattern design.
Along with the pan is the oil pan drain plug, this gets removed and reinstalled quite frequently and can be
torqued down to 15 ft-lbs.
Toyota Prius Oil Pan Torque Specs : 8 ft-lbs
Toyota Prius Oil Drain Plug Torque Specs : 15 ft-lbs
Valve Covers Installation
The valve cover installation is rather simple, there are rubber seals for each bolt hole and a silicone gasket
that prevents oil from leaking out of the engine. It is recommended to replace both the seals
and the gaskets although if they are in good condition you can reuse them. If you do choose to reuse them I
would use some silicone sealant along with the silicon gasket to ensure it does not leak.
The valve cover bolts torque down to 106 in-lbs or about 8 ft-lbs in a criss cross order. Be sure not to miss
any bolts to avoid having oil leak out onto the exhaust pipes and cause a lot of smoking.
Toyota Prius Valve Cover Torque Specs : 8 ft-lbs
Intake Manifold and Fuel Rail Installation
When installing the intake manifold you want to make sure you have all the surfaces as well as intake holes
cleaned out before placing the manifold into position. Once cleaned you can then place
the intake manifold gaskets onto the alignment pins. If you want you can also use a little bit of sealant on the
gaskets to help ensure there are no leaks. With the gaskets in place you can now put
the manifold down onto the gaskets and begin to install the bolts. The intake manifold bolts torque to 21 ft-lbs
and can be tightened starting from the inside and going outwards. The COPs or the coils
for the spark plugs get torqued down to 60 in-lbs or about 5 ft-lbs and the spark plugs themselves can be
torqued down to 13 ft-lbs, be careful not to overtorque these as they can snap and cause big problems.
When installing the fuel rail make sure that all the fuel injectors are in good condition and that all the
o-rings are in place and
are in good condition. If everything is good you can place the fuel rail into position and push the injectors
into their holes and start to torque the rail bolts to 90 in-lbs or about 8 ft-lbs.
Toyota Prius Intake Manifold Torque Specs : 21 ft-lbs
Toyota Prius Ignition Coil Torque Specs : 5 ft-lbs
Toyota Prius Spark Plug Torque Specs : 13 ft-lbs
Toyota Prius Fuel Rail Torque Specs : 8 ft-lbs
Exhaust Manifold Installation
The exhaust manifold can be installed by cleaning the surface areas on both the head an the manifold itself and
then by using the exhaust manifold gasket and putting it in place. Once the gasket is in its
location you can put the manifold onto the heads and begin to torque the fasteners down to 27 ft-lbs. I always use some
copper spray from permatex on the exhaust manifold gaskets to ensure I do not end up with
any exhaust leaks once done. When you go to install the engine into the vehicle or if it is already in the
vehicle the torque specs for the exhaust manifold to the exhaust pipes or catalytic converter is 35 ft-lbs.
The EGR system consists of a series of pipes that range from the manifold to the head. All of the EGR pipes can be tightened down
to 14 ft-lbs.
Toyota Prius Exhaust Manifold Torque Spec : 27 ft-lbs
Toyota Prius Exhaust Pipe Torque Specs : 35 ft-lbs
Toyota Prius EGR Pipe Torque Specs : 14 ft-lbs
Water Pump and Thermostat Installation
The water pump on the Toyota 1.8L engine should be installed by using
a new gasket and if desired some silicon sealant to help prevent leaks. Be sure to clean both metal surfaces prior to installing the pump. Once
prepared the pump can be moved into placed and the bolts should be torqued to 8 ft-lbs.
Toyota Prius Water Pump Torque Specs : 8 ft-lbs
Front Dress and Pulley belt Installation
Most of what is left on the engine is just place and tighten objects such as the belt pulleys, belt tensioner,
throttle body, oil filter neck, crankshaft pulley, and motor mounts. If the items have a gasket and hold either
oil or coolant inside the engine then feel free to add some sealant along with the gasket. Always be sure to
inspect your gaskets and replace them if there is any deteriation or flaws with them. For the
belt system the crankshaft pulley gets torqued to 140 ft-lbs. The belt
tensioner assembly can be tightened to 51 ft-lbs. When installing be sure
it turns smoothly and if it does not then replace it with a new one as the bearing can go bad. The engine
motor mount can be installed onto the engine block if it hasn't been already, the torques for
the mount to the block is 59 ft-lbs and then when installing the mount to the vehicle or frame it can be torqued to
35 ft-lbs. Finally the throttle body can be installed on top of the intake manifold
with a good gasket and some added sealant using 7 ft-lbs in a criss cross pattern. For installing the belt you
can use a tool to move the tensioner into its springed state and install the belt as shown in the
picture. The power steering pump should be tightened down to 27 ft-lbs. The A/C compressor can be tightened
down to 18 ft-lbs.
Toyota Prius Crankshaft Pulley Torque Specs : 140 ft-lbs
Toyota Prius Belt Tensioner Torque Specs : 51 ft-lbs
Toyota Prius Motor Mount to Engine Torque Specs : 59 ft-lbs
Toyota Prius Motor Mount to Frame Torque Specs : 35 ft-lbs
Toyota Prius Power Steering to Engine Torque Specs : 27 ft-lbs
Toyota Prius A/C Compressor Torque Specs : 18 ft-lbs
